The latest figures from SA Health for last year show that about 22 per cent of Port Pirie's children under the age of five have blood lead levels above World Health Organisation guidelines.

The number of children in the high risk category has however dropped slightly.

The Director of Public Health Kevin Buckett said the figures also show the average blood lead level for children aged two has risen for the first time since 2005.

He said this is concerning because a child's blood lead level usually starts to drop at that age.

"It does indicate that we've got to really do more things to get blood leads down."

Mr Buckett said results are likely to remain that way until emissions from the smelter reduce.

"Once transformation happens and the smelter is modernised it will be a much cleaner site in terms of site contamination, so it will be new technology rather than the old technology that's there at the moment.

"That will bring air levels down and we're predicting confidently that will have a major impact on reducing blood leads in children in the population."

Mr Buckett said once this happens, it will be able to focus more on early prevention and targeting of children with extremely high blood lead levels.

"Because there will be far fewer children affected overall, we'll be able to have a much more targeted program that should see us get all children below 10 micrograms a decilitre."

The smelter re-development is still awaiting final approvals from State Cabinet.